Tension spring device

ABSTRACT

A tension spring device which can be used for mooring boats and towing cars comprises a flexible draw element, for example, a rope, and a spring element of an elastic material, for example, rubber. Between its ends the draw element is connected with the spring element at at least two points and between these two points the draw element extends in a path deviating from a straight line, for example, a helix path, the draw element engaging the elastic material of the spring element at least in the tensioned state of the spring device.

United States Patent [191 Derman et a1.

[ TENSION SPRING DEVICE [76] Inventors: Karl Gustav Einar Demian,

Sorgardsvagen 7, S-433 00 Partille; Nils-Erik Bohman, Sveavagen 8 A, S-331 00 Varnamo, both of Sweden [22] Filed: Sept. 29, 1972 [21] Appl. No.: 293,365

[30] Foreign Application Priority Data Sept. 30, 1971 Sweden ..l2358/71 Dec. 19,1971 Sweden ..l5843/71 Apr, 7, 1972 Sweden [52] US. Cl. 267/74 [51] Int. Cl Fl6f 1/46 [58] Field of Search 267/74, 73, 69

[56] References Cited UNITED STATES PATENTS 2,364,081 l2/1944 Lambert 267/69 1".f.'l'li"'..','flf'i'lr June 18, 1974 2,991,524 7/1961 Dobrikin 267/69 3,549,143 12/1970 Gilliam ..267/74 Primary Examiner-James B. Marbert Attorney, Agent, or Firm-Albert L. Jeffers; Roger M. Rickert [57] ABSTRACT A tension spring device which can be used for mooring boats and towing cars comprises a flexible draw element, for example, a rope, and a spring element of an elastic material, for example, rubber. Between its ends the draw element is connected with the spring element at at least two points and between these two points the draw element extends in a path deviating from a straight line, for example, a helix path, the draw element engaging the elastic material of the spring element at least in the tensioned state of the spring device.

12 Claims, 10 Drawing Figures PATENTEDJuM 18 m4 SHEET l U? 3 PATENTEDJUN 18 I974 SHEET 2 or 3 PATENTEnJun 18 I974 8 l SHEET 3 or 3 slisi ian vl 1 TENSION SPRING DEVICE BACKGROUND OF THE INVENTION The present invention relates to a tension spring device which can be used for example as a towing or mooring device or for maintaining a constant tension in for example a tent rope, comprising a flexible draw element, for example a rope, a cable or a chain, and an elastic spring element.

It is often desirable to provide a rope, a cable, a chain or the like with a spring element for taking up the tensile stresses so that strong pulls in the rope, cable or chain are avoided or the rope, cable or chain can be maintained in a substantially constant tension. This is of great importance for example when the rope, cable or chain is to be used for towing or for the mooring of boats and as a tent rope.

For many reasons it is preferable to use a spring element consisting of a highly elastic material, such as rubber, because of the fact that the spring motion is soundless and that no scraping of for example a boat takes place. Because of the relatively small values of the tensile and tearing strength of rubber it is not suitable to use a rubber spring in the same way as a metal spring.

The object of the invention is to provide a, tension spring device having a spring element consisting of highly elastic material, such as rubber.

SUMMARY OF THE INVENTION In accordance with the invention there is provided a tension spring device comprising a flexible draw element and an elastic spring element, in which the draw element is at at least two points connected with the elastic springelement and between these two points extends along a path deviating from a straight line and in which the draw element, at least in the tensioned state of the tension spring device, engages said spring element between said two points.

An embodiment of a tension spring device of this kind includes a rubber body as the spring element and a draw element, preferably a. rope, which extends into the. rubber body at one end thereof, out to the periphery of the rubber body, helically around the body, into the rubber body and out therefrom at the opposite end of the rubber body.

It is preferred that the draw element is fixed or locked to the spring element at said connection points. Thereby it is secured that the tension spring device returns to the original position after it has been subjected to a tensional force. The draw element can be locked to the spring element in such a way that in the nontensioned position of the tension spring device the draw element extends around the spring element at some distance therefrom.

It is also possible to provide the periphery of the spring element with a helical, outwards open groove in which the draw element is positioned.

Especially when the tension spring device shall be able to resist great tensional forces it is suitable to position the draw element within the spring element between said points of connection. Preferably a tension spring device of this kind is constituted by a rubber body into which a cable is vulcanized over a portion of its length, the portion of the cable positioned within the rubber body extending in loops or the like. The loops BRIEF DESCRIPTION OF THE DRAWING:

FIG. 1 shows an embodiment of a tension spring device in accordance with the invention;

FIG. 2 shows an end portion of a spring element of another embodiment of the tension spring device in accordance with the invention;

FIG. 3 is a section of the end portion of the spring element of a further embodiment of a tension spring device in accordance with the invention;

FIG. 4 shows the end portion of a spring element of a further tension spring device according to the invention;

FIG. 5 is a section of the end portion shown in FIG. 4 and a rope extending therethrough;

FIG. 6 shows a reinforcing element for the end portion of FIGS. 4 and 5;

FIG. 7 is a section of the end portion of a spring element provided with a reinforcing element of the kind shown in FIG. 6; and

FIGS. 8, 9 and 10 show alternative embodiments of the spring device in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT:

The spring device shown in FIG. 1 can be used as a mooring or towing device. The spring device comprises a draw element, for example, a rope 2 of conventional type, and a spring element 4 preferably consisting of rubber. The spring element 4 is I substantially bar shaped and has a cylindrical central portion 6 and two enlarged end portions 8. Each end portion 8 consists of two conical portions having coincident base surfaces. A hole 10 extends through each end portion and has its end openings positioned at the free end surface 11 of the outer conical portion 12 and the jacket surface of the inner conical portion 14, respectively. Adjacent the openings in the end surfaces 11 the holes 10 extend substantially axially with respect to the spring element and successively merge into a helical path in the direction of their other openings. The rope 2 extends into the hole 10 and out onto the cylindrical central portion 6 of the spring element, where the rope helically extends the desired number of turns around the jacket surface of the cylindrical central portion 6. Thereupon the rope extends into the hole 10 at the opposite end portion 8 of the spring element and extends out from this end portion in the axial direction. When the draw element, i.e., the rope, is subjected to a tensional force at opposite sides of the spring element 4, the turns of the rope extending around the central portion 6 will elastically press the central portion 6 together at the same time as the end portions are separated from each other and turned in relation to each other in such a direction that a slight rolling up of the turns takes place.

Thereby, there is provided a spring action comprising a combination of pressure, tensile and torsion stress on the spring element.

In FIG. 2 there is shown another embodiment of the spring element. Also, this spring element 16 is substantially bar shaped and has a substantially cylindrical central portion 18 and enlarged end portions 20 of which only one is shown. The end portions 20 have a hole 22 extending transversely in relation to the axis of the spring element. The rope 2 extends through said hole 22. From the hole 22 the rope extends helically a desired number of turns around the cylindrical central portion 18 in substantially the same way as in the embodiment shown in FIG. 1. As mentioned, the spring element 16 is provided at its oppsite end with an end portion of the same design as the end portion 20, this other end portion being provided with a corresponding hole through which the rope extends. The function of the tension spring device of FIG. 2 is substantially the same as the function of the device of FIG. 1.

In certain cases it can be advisable with regard to the strength to provide the spring with end inserts of a harder material, for example, plastic, than the rest of the spring element which preferably consists of rubber, as shown in FIG. 3. FIG. 3 is a section through one end of a spring element of this kind. The insert 24 is provided with a hole 28 which can have the same design as the hole of the embodiment of FIG. 1. The hole 28 merges into a hole 30 in the wall of the rubber element 26. The insert 24 has a portion 32 which is insertable into a corresponding cavity in the end portion of the rubber element. The rope 2 extends into and around the spring element in the same way as the ropes of the embodiments of FIGS. 1 and 2.

In an embodiment of the tension spring device the draw element, i.e., the rope in the shown case, is fixedly connected with the spring element, i.e., the rubber body, at the ends of said portion deviating from a straight line.

In FIGS. 4 and 7, inclusive, there is shown how the rope can be connected with a rubber spring element when it is desired to provide for a locking of the rope in relation thereto. The end portions of the spring element are designed in the same way for which reason there is shown only one of the end portions in FIGS. 4, and 7. The end portion of the spring element 36 is provided with three parallel holes 38 through which the rope 40 extends substantially in a loop configuration. As appears especially from FIG. 4, the rubber material between the adjacent ends of two holes positioned beside each other is removed for constituting grooves 42 and 44 for receiving at least a portion of the section of the rope. At the hole adjacent the free end of the spring element there is a similar groove 46 and at the hole positioned at the greatest distance from the free end there is a declined groove 48 merging into a helix path along which the rope shall extend between the end portions of the spring element.

In order to increase the strength of the end portion it can be suitable to provide each of these portions with a reinforcing element 50 of the kind shown in FIG. 6. The reinforcing element 50 is vulcanized into the rubber as shown in FIG. 7, i.e. so that the holes of the reinforcing element, which have somewhat greater diameter than the holes of spring element are concentrically positioned in relation thereto.

The connection of the rope to the spring element in accordance with the embodiment shown in FIGS. 4 to 7, inclusive, provides for a locking of the rope in relation to the spring element, so that no sliding of the rope in relation to the spring element tkes place when the tension spring device is subjected to a tensional force. This provides for a complete return to the original position when the tensional force ceases.

Said locked connection of the rope to the spring element can be provided also by other means for example by connecting the rope to the ends of the spring element by means of half hitches.

In the case that the rope is locked to the ends of the spring element, the rope can extend in such a way between the connections with the spring element that in the non-tensioned position of the tension spring device the rope is positioned at some distance from the cylindrical central portion of the spring element.

In the embodiment of the invention shown in FIG. 8 the rope 52 is positioned in an outwards open helical groove 54. Thereby the rope is protected from damage. Besides, there is obtained a somewhat different spring characteristic of the tension spring device, as no sliding of the rope along central portion of spring element can take place. Thus, the tension spring device of FIG. 8 has a somewhat less progressive characteristic than the embodiment of FIG. 1. Also in the embodiment shown in FIG. 8 the rope can be connected with the ends of the spring element by means of a device of the kind shown in FIGS. 4 to 7, inclusive. The rope can extend so in relation to the spring element that in the nontensioned position of the tension spring device the rope extends at some distance from the bottom of the groove.

In FIG. 9 there is shown a tension spring device especially suitable in the case that the tension spring device shall be able to take up great tensional forces. This device can consist of a wire 56 having a portion of its length enclosed in an element of elastic material 58. Preferably the elastic material consists of rubber, and preferably the wire 56 is vulcanized into the rubber in a helical path. However, the wire can extend in another path deviating from the straight line, for example a sinusoidal path. In the case that the rope is vulcanized into the rubber there is usually not required any special locking of the rope to the rubber at the ends of the rubber body, but of course it is possible also in this case to provide a secure locking of the rope to the rubber body at the ends thereof by means of any locking device. A tension spring device of this kind is very stiff when normal rubber qualities are used for the elastic spring element.

FIG. 10 shows another tension spring device in which a portion or the draw element is enclosed in the spring element. The draw element consists of a chain 60, the links 62 of which are pivotally connected with each other. A portion of the chain 60 is enclosed by an elastic material, preferably rubber, for constituting an elastic spring element 64. The chain 60 is enclosed in the spring element 64 in such a way that at least in the nontensioned state of the tension spring device the links of the chain are angularly positioned in relation to each other. Thus, the chain 60 extends in zigzag configuration in the spring element.

The invention can be modified within the scope of the following claims.

We claim:

l. A tension spring device comprising an elastic spring member having end portions and a central portion, and a flexible elongated draw member at spaced sections of its length connected with said end portions and extending continuously between said end portions in a helical path around said central portion of the spring device, said draw member engaging between said spaced sections said central portion of the spring member at least in a tensioned state of said spring device.

2. A tension spring device as claimed in claim 1, in which said central portion is of cylindrical shape.

3. A tension spring device as claimed in claim 1, comprising means for indisplacably locking said spaced sections of said draw member to said end portions.

4. A tension spring device as claimed in claim 3, said locking means locking said two spaced sections of the draw member to said end portions in such a way that said draw member extends in spaced relationship to said central portion in the non-tensioned state of said tension spring device and engages said central portion in the tensioned state of said tension spring device.

5. A tension spring device as claimed in claim 3, said locking means locking said two spaced sections of the draw member to said end portions in such a way that said draw member engages said central portion between said spaced sections in the non-tensioned as well as the tensioned state of said tension spring device.

6. A tension spring device as claimed in claim 3, in which each of said end portions forms at least two substantially parallel holes constituting said means for indisplacably locking said draw element to said end portions said draw element extending in a loop through said holes.

7. A tension spring device as claimed in claim 3, said end portions comprising reinforcing elements.

8. A tension spring device as claimed in claim 1, in which said central portion forms an outward open, helical groove, said draw member extending at least partially received in said groove between said end portions of the spring member.

9. A tension spring device comprising a spring member of a highly elastic material and a flexible, elongated draw member having a section of its length extending through said spring member along a path deviating from a straight line, substantially all surface portions of said section being enclosed by and fixedly connected with said highly elastic material.

10. A tension spring device as claimed in claim 9, in which said section of the draw element extends helically within the spring member.

11. A tension spring device as claimed in claim 9, in which said section of the draw element extends sinusoidally within said spring member.

12. A tension spring device comprising a spring member of a highly elastic material and a chain comprising pivotally connected links, a section of said chain being positioned within said spring member, said chain links of said chain section being angularly disposed in relation to each other at least in the non-tensioned state of the tension spring device. 

1. A tension spring device comprising an elastic spring member having end portions and a central portion, and a flexible elongated draw member at spaced sections of its length connected with said end portions and extending continuously between said end portions in a helical path around said central portion of the spring device, said draw member engaging between said spaced sections said central portion of the spring member at least in a tensioned state of said spring device.
 2. A tension spring device as claimed in claim 1, in which said central portion is of cylindrical shape.
 3. A tension spring device as claimed in claim 1, comprising means for indisplacably locking said spaced sections of said draw member to said end portions.
 4. A tension spring device as claimed in claim 3, said locking means locking said two spaced sections of the draw member to said end portions in such a way that said draw member extends in spaced relationship to said central portion in the non-tensioned state of said tension spring device and engages said central portion in the tensioned state of said tension spring device.
 5. A tension spring device as claimed in claim 3, said locking means locking said two spaced sections of the draw member to said end portions in such a way that said draw member engages said central portion between said spaced sections in the non-tensioned as well as the tensioned state of said tension spring device.
 6. A tension spring device as claimed in claim 3, in which each of said end portions forms at least two substantially parallel holes coNstituting said means for indisplacably locking said draw element to said end portions said draw element extending in a loop through said holes.
 7. A tension spring device as claimed in claim 3, said end portions comprising reinforcing elements.
 8. A tension spring device as claimed in claim 1, in which said central portion forms an outward open, helical groove, said draw member extending at least partially received in said groove between said end portions of the spring member.
 9. A tension spring device comprising a spring member of a highly elastic material and a flexible, elongated draw member having a section of its length extending through said spring member along a path deviating from a straight line, substantially all surface portions of said section being enclosed by and fixedly connected with said highly elastic material.
 10. A tension spring device as claimed in claim 9, in which said section of the draw element extends helically within the spring member.
 11. A tension spring device as claimed in claim 9, in which said section of the draw element extends sinusoidally within said spring member.
 12. A tension spring device comprising a spring member of a highly elastic material and a chain comprising pivotally connected links, a section of said chain being positioned within said spring member, said chain links of said chain section being angularly disposed in relation to each other at least in the non-tensioned state of the tension spring device. 